main(List<String> args) {
  // 默认参数值
  printPerson('李四');
  printPerson('李四', age: 20);
  printPerson('李四', gender: 'Male');
}

printPerson(String name, {int age = 30, String gender = 'Female'}) {
  print('name=$name,age=$age,gender=$gender');
}
